Field of the Invention
The invention relates in general to the field of signal processing, and more particularly to an eye pattern measurement apparatus, and a clock and data recovery system and method thereof.
Description of the Related Art
In data communications such as high-speed serial data communications, to save resources, usually only data signals, but not clock signals synchronous with the data signals, are transmitted. Thus, to ensure synchronization of data processing, a data receiving terminal needs to extract timing information such as a clock from the received data, so as to further perform “re-timing” on the data by using the clock to eliminate jittering accumulated during the transmission process. This process of extracting the clock and data re-timing is referred to as “clock and data recovery” (CDR).
Further, for data obtained from transmission, eye quality of an eye pattern of the data usually needs to be measured to obtain the performance of the data transmission system. Currently, the eye pattern measurement directly outputs scan data, which is acquired from sampling by using multiple different clock signals having a period equal to the period of the above extracted clock signal, and the eye quality of the received data is then obtained accordingly. However, the scan data in fact is asynchronous from the above extracted clock signal, and the subsequent sampling of the scan data by using the extracted clock signal may fail to satisfy a setup/hold time requirement, leading to synchronization data errors.